System and method for providing power and control through a rotating interface

ABSTRACT

Embodiments of the present invention provide a system ( 10 ) operable to provide power and control through a rotating interface. The system ( 10 ) generally includes a control unit ( 12 ) and a distributor unit ( 14 ). The control unit ( 12 ) is operable to generate a power signal having a plurality of power transitions. The distributor unit ( 14 ) is operable to rotatably couple with the control unit ( 12 ), receive the power signal from the control unit ( 12 ), identify power transitions within the power signal, and generate a plurality of output signals corresponding to the identified power transitions. The distributor unit ( 14 ) is also at least substantially powered by the power signal to enable generation of the output signals.

RELATED APPLICATION

The present non-provisional application claims the benefit of U.S.Provisional Application No. 60/739,721, entitled “SYSTEM AND METHOD OFICE PROTECTION POWER AND CONTROL THROUGH A ROTATING INTERFACE USING AMINIMUM OF CONDUCTORS,” filed Nov. 23, 2005. The identified provisionalapplication is incorporated herein by specific reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to systems and methods forproviding power and control through a rotating interface. Moreparticularly, various embodiments of the present invention relate tosystems and methods that provide power and control through a rotatinginterface by utilizing power transitions within a power signal.

2. Description of the Related Art

It is often desirable to provide power and control signals through arotating interface. For example, rotary components such as aircraftpropeller blades often include a plurality of electrical deicingelements for ice protection. To provide power and control to each ofthese deicing elements, conventional systems require at least one slipring to be employed for each control and power line. Although attemptshave been made to provide power and control signals through a singleconductor in a rotating interface, and therefore limit the number ofrequired slip rings, such attempts have required complicated digitalsignal modulation, which increases system complexity and provides poorfunctionality in noisy environments.

SUMMARY OF THE INVENTION

Embodiments of the present invention solve the above-described problemsand provide a distinct advance in the art of power and control systems.More particularly, various embodiments of the invention relate tosystems and methods that provide power and control through a rotatinginterface by utilizing power transitions within a power signal.

In one embodiment, the system generally includes a control unit and adistributor unit. The control unit is operable to generate a powersignal having a plurality of power transitions. The distributor unit isoperable to rotatably couple with the control unit, receive the powersignal from the control unit, identify power transitions within thepower signal, and generate a plurality of output signals correspondingto the identified power transitions. The distributor unit is also atleast substantially powered by the power signal to enable generation ofthe output signals.

Other aspects and advantages of the present invention will be apparentfrom the following detailed description of the preferred embodiments andthe accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Preferred embodiments of the present invention are described in detailbelow with reference to the attached drawing figures, wherein:

FIG. 1 is a schematic diagram of a system configured in accordance withvarious embodiments of the present invention;

FIG. 2 is an exemplary timing diagram corresponding to the system ofFIG. 1;

FIG. 3 is a perspective view of a control unit operable to be utilizedby various embodiments of the present invention;

FIG. 4 is a perspective view of a distributor unit operable to beutilized by various embodiments of the present invention;

FIG. 5 is a schematic diagram of an exemplary power control stagecomprising a portion of the control unit of FIG. 3;

FIG. 6 is a schematic diagram illustrating a circuit comprising aportion of the distributor unit of FIG. 4;

FIG. 7 is a schematic diagram of power control elements that comprise aportion of the circuit of FIG. 6;

FIG. 8 is a schematic diagram of the circuit of FIGS. 6-7 showingportions of the power control elements in more detail;

FIG. 9 is a schematic diagram of a system configured in accordance withvarious other embodiments of the present invention;

FIG. 10 is a schematic diagram of a rectifier assembly operable to beutilized by various embodiments of the system of FIG. 9;

FIG. 11 is a schematic diagram of an autotransformer operable to beutilized by various embodiments of the system of FIG. 9; and

FIG. 12 is a diagram illustrating various propeller regions andcorresponding heating zones.

The drawing figures do not limit the present invention to the specificembodiments disclosed and described herein. The drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of various embodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following detailed description of the invention references theaccompanying drawings that illustrate specific embodiments in which theinvention can be practiced. The embodiments are intended to describeaspects of the invention in sufficient detail to enable those skilled inthe art to practice the invention. Other embodiments can be utilized andchanges can be made without departing from the scope of the presentinvention. The following detailed description is, therefore, not to betaken in a limiting sense. The scope of the present invention is definedonly by the appended claims, along with the full scope of equivalents towhich such claims are entitled.

Turning now to the drawing figures, and particularly FIGS. 1-12, a powerand control system 10 is shown constructed in accordance with variouspreferred embodiments of the present invention. The system 10 broadlycomprises a control unit 12 and a distributor unit 14 operable to berotatably coupled with the control unit 12. As is discussed in moredetail below, the control unit 12 is operable to mount to a staticportion of an aircraft, the distributor unit 14 is operable to mount toa rotating portion of the aircraft, such as a propeller, and the controlunit 12 is operable to provide a power signal to the distributor unit 14for power and control purposes.

The control unit 12 is operable to electrically couple with an aircraftpower supply to receive power from the aircraft. Preferably, the controlunit 12 is operable to receive electric power from the aircraft. Thecontrol unit 12 is additionally operable to electrically couple with theaircraft to transmit and receive control signals to enable the aircraft,or its operators, to control and monitor the functionality of the system10.

The control unit 12 preferably comprises a controller 16 and powerconditioning elements 18. The controller 16 and power conditioningelements 18 are generally operable to generate a power signal having aplurality of power transitions. As is discussed in more detail below,the power signal may comprise a three-phase alternating current signalin delta or wye configurations, a one-phase alternating current signal,and/or a direct current signal. The power transitions preferablyrepresent on-off, off-on, on-off-on, off-on-off, etc., transitionswithin the power signal. However, the power transitions may representany combination of on and off power transitions are not limited to thosearticulated above.

For example, in some embodiments where the power signal is an AC signal,the power transitions may comprise on and off periods. Specifically, thepower transitions may comprise on and off periods corresponding to oneor more cycles of the AC power signal. Thus, the power transitions donot necessarily comprise rapid power transitions.

The controller 16 may comprise various computing devices,microprocessors, microcontrollers, digital signal processors,programmable logic devices, integrated circuits, discrete digital andanalog logic elements, combinations thereof, and the like. Thecontroller 16 is also preferably operable to provide fault detection andcontrol of fault related activities, handle communication with theaircraft, and relay diagnostic information. The power conditioningelements 18 may comprise any component or combination of componentsoperable to generate the desired power signal based on instructions fromthe controller 16 and the power provided by the aircraft.

Further, the controller 16 may be operable to control the variousfunctions of the system 10 according to a computer program, includingone or more code segments or other instructions, or with variouscontroller logic and structure.

The computer program may comprise a plurality of code segments arrangedas an ordered listing of executable instructions for implementinglogical functions in the controller 16. The computer program can beembodied in any computer-readable medium, including a memory, for use byor in connection with an instruction execution system, apparatus, ordevice, such as a computer-based system, processor-containing system, orother system that can fetch the instructions from the instructionexecution system, apparatus, or device, and execute the instructions.

In the context of this application, a “computer-readable medium” can beany means that can contain, store, communicate, propagate or transportthe program for use by or in connection with the instruction executionsystem, apparatus, or device. The computer-readable medium can be, forexample, but not limited to, an electronic, magnetic, optical,electro-magnetic, infrared, or semi-conductor system, apparatus, device,or propagation medium. More specific, although not inclusive, examplesof the computer-readable medium would include the following: anelectrical connection having one or more wires, a portable computerdiskette, a random access memory (RAM), a read-only memory (ROM), anerasable, programmable, read-only memory (EPROM or Flash memory), anoptical fiber, a compact disc (CD), a digital video disc (DVD),combinations thereof, and the like. The computer-readable medium couldeven be paper or another suitable medium upon which the program isprinted, as the program can be electronically captured, via forinstance, optical scanning of the paper or other medium, then compiled,interpreted, or otherwise processed in a suitable manner, if necessary,and then stored in a memory.

Preferably, the power conditioning elements 18 include a power controlstage 20 to control the generation of the power signal provided to thedistributor unit 14 and to define the plurality of power transitionswithin the power signal. In some embodiments, the power control stage 20may comprise one or more conventional relays or switches operable to befunctioned by the controller 16 to repeatedly open and close to providethe desired power transitions within the power signal. However, in someembodiments the use of conventional relays and switches may beundesirable due to reliability issues resulting from their frequentfunctioning, the switching time involved, and/or due to EMI/EMCconsiderations.

Consequently, the power control stage 20 preferably includes at leastone solid-state switching element 22 to form the power signal andassociated power transitions. In various embodiments, the solid-stateswitching element 22 includes at least one silicon-controlled rectifier(SCR) 24 to provide the desired power transitions. The SCR 24, alsocommonly referred to as a thyristor, is operable to controllably turn onand off to allow the flow of current. Thus, through repeated switchingof the SCR 24, and/or other power conditioning elements 18, the system10 is operable to generate the power signal including the plurality ofpower transitions.

In some embodiments, the power control stage 20 may include a pluralityof SCRs 24. For instance, the power control stage 20 may include a TRIACto regulate current flow. As is known in the art, a TRIAC (triode foralternating current) presents approximately the same configuration astwo SCRs joined in an inverse parallel configuration with their gatesconnected together.

However, due to the high-frequency limitations and voltage sensitivityof TRIACs, it is preferable to configure the SCRs 24 in a back-to-backconfiguration as shown in FIG. 5. The use of the SCRs 24 instead ofTRIACs, alternistors, insulated gate bipolar transistors (IGBT), andother solid-state components is desirable as the use of the SCRs 24allows for better thermal management, more rugged construction, andhigher voltage and current tolerances.

In the back-to-back SCR configuration, each SCR 24 is preferably drivenusing an isolated constant current gate drive formed from the transistorconfiguration shown in FIG. 5. The gate drive current is preferablyapproximately 30 mA to ensure activation under a wide range ofconditions, tolerances, and temperatures. When commanded “on”, constantcurrent is directed through the SCR 24, the SCR 24 is held “on”, and theSCR 24 rapidly conducts for the proper polarity of incoming alternatingcurrent signals. If the alternating current signals are of the oppositepolarity then the SCR 24 is perched and ready to rapidly conduct whenthe alternating current polarity changes with no or minimal delay.

To commutate the SCR 24, the constant current is shunted across the gateand cathode through optoisolators to ensure that the SCR 24 willcommutate upon the zero current crossing. Further, the general immunityof the SCR 24 to false triggering and noise is greatly enhanced by thefact that the gate and cathode are essentially shorted together whencommanded off.

The perched SCR configuration of FIG. 5 desirably allows one of the SCRs24 to be held on prior to the commutation of the companion SCR 24 andthus the commutating SCR is free to recover as the other SCR isgenerally instantly ready for conduction. Such a configuration masks thereverse recovery characteristics of the commutating SCR and eliminatesthe reverse recovery associated radio-frequency noise. Also generallyeliminated is the small turn-on conduction angle associated withconventional gate drive configurations in which the gate drive isessentially bootstrapped to the supply, thus requiring a minimum phasevoltage to develop before there is sufficient current to trigger thegate.

Preferably, the power control stage 20 includes a snubber 25 placedacross each pair of SCRs 24 provided by the power control stage 20. Thesnubber 25 preferably includes a capacitor and a resistor. The capacitorprovides snubbing functionality while the resistor limits the surgecurrent through the capacitor during the transient. The resistor alsoacts to dampen responses and preferably has a resistance in the range of1 to 900 ohms. Preferably, the snubber 25 is operable to limit leakagecurrent to less than 3.5 mA at 400 Hz for safety reasons.

The power control stage 20 may also include a transient protectiondevice 26 such as a metal oxide varistor (MOV) or a gas discharge tube(GDT) coupling the output of the SCRs 24 to ground. The use of thetransient protection device 26 may be desirable in aircraft environmentsto provide lighting protection. For example, the transient protectiondevice 26 may be configured to activate at voltages above the normal ACsupply but below the maximum withstand voltage of the SCRs 24. Anytransients activating the transient protection device 26 would then beshunted to ground.

The SCR 24 configuration shown in FIG. 5 generally implements asolid-state relay (SSR) channel. Preferably, the power control stage 20includes a SSR channel, and thus two SCRs 24 configured as discussedabove, for each phase within the power signal provided to thedistributor unit 14. Thus, in embodiments where the control unit 12provides three-phase power to the distributor unit 14, the power controlstage 20 may include three SSR channels, and thus three pairs of SCRs 24configured as discussed above. However, as should be appreciated, thepower control stage 20 may include any number or any configuration ofswitching elements and is not limited to the back-to-back SCRconfiguration discussed above.

In embodiments where a delta three-phase arrangement is provided whereonly two of the three phases require power control, power dissipation inthe power control stage 20 can be minimized if control is provided ononly two of the three phases. Isolation of the third phase may beensured when the unit is off or in response to fault conditions.

In some embodiments, the controller 16 additionally includes a watchdogtimer 28 and a failsafe monitor 30. The watchdog timer 28 is operable toprovide independent status monitoring of the system 10 and control unit12. For instance, the watchdog timer 28 may be operable to monitor thestatus of the controller 16 and the integrity of the controller 16 powersupply. The watchdog timer 28 is operable to reset the controller 16should it identify a fault and/or actuate or deactivate various system10 elements, such as the EIR discussed below, to ensure safe system 10functionality.

The failsafe monitor 30 is operable to monitor the temperature of thecontrol unit 12 and/or monitor the current provided by the powerconditioning elements 18. The failsafe monitor 30 is preferablyelectrically independent from the controller 16 logic and is operable tofunction the EIR, discussed below, in response to a detected fault.

The controller 16 also preferably includes an aircraft communicationinterface 32. The aircraft communication interface 32 enables thecontrol unit 12 to communicate with the aircraft to transmit and receiveinstructions and information therefrom. The aircraft communicationinterface 32 may include ARNIC-429, MIL-STD-1553, CAN, and other bussesto enable communication with the aircraft. Utilizing the aircraftcommunication interface 32, the controller 16 may transmit and receivesignals and parameters such as operating mode, outside air temperature,airspeed, propeller speed, deicing instructions and control, etc. Asshould be appreciated, the aircraft communication interface 32 mayinclude any wired or wireless connections for communicating with theaircraft to transmit and receive any signals and information therefrom,and is not necessarily limited to the busses discussed above.

In some embodiments, the controller 16 may also include an input/outputinterface 34 to receive inputs and provide outputs independent of theaircraft communication interface 32. For example, the input/outputinterface 34 may be operable to provide backup or redundantcommunications with the aircraft in the event of the failure of theaircraft communication interface 32.

The controller 16 may also include a maintenance interface 36 to allowdirect access to controller information, such as fault logs, to assistin manufacturing and component defect investigations. The maintenanceinterface 36 is operable for coupling with external diagnosticequipment, such as a personal computer or test jig, using readilyaccessible protocols such as RS232. The maintenance interface 36 ispreferably transparent to the aircraft.

The power conditioning elements 18 may include any element orcombination of elements operable to facilitate generation of the powersignal and powering of system 10 components including the control unit12 and distributor unit 14. In some embodiments, the power conditioningelements 18 may include an input voltage monitor 38, an emergencyisolation relay (EIR) 40, an EIR voltage monitor 42, a power controlvoltage monitor 44, current sensing elements 46, and/or a DC powersupply 48.

The power conditioning elements 18 are coupled with the aircraft toreceive power therefrom. Preferably, the power conditioning elements 18are coupled with the aircraft to receive three-phase electrical powerand DC power therefrom, condition the received power, and form the powersignal as discussed herein. However, the power conditioning elements 18may receive any form of electrical energy from the aircraft for any useby the system 10 and generation of the power signal.

The input voltage monitor 38 is operable to monitor the power providedby the aircraft to the control unit 12. Preferably, the input voltagemonitor 38 is operable to monitor the power provided by the aircraft toensure that the input power is within acceptable limits. The inputvoltage monitor 38 may be further operable to communicate with thecontroller 16 to provide status information thereto. Preferably, theinput voltage monitor 38 is electrically isolated from the powerprovided by the aircraft, and thus employs optocouplers, miniaturetransformers, or other similar devices to monitor input voltages,current, and/or power.

The EIR 40 is preferably coupled with the power control stage 20 toisolate fault conditions. The EIR 40 may be configured to prevent asingle power failure from resulting in uncontrolled application of powerto the distributor unit 14. The reliability of the EIR 40 is preferablyenhanced by not being integral with the power control stage 20, and thusis not required to switch frequently.

The EIR voltage monitor 42 is operable to monitor the output from theEIR 40 to ensure that all phases are open when the EIR 40 isde-energized and to ensure that all phases are closed when the EIR 40 isenergized. The EIR voltage monitor 42 is preferably coupled with thecontroller 16 to provide status information thereto. Preferably, the EIRvoltage monitor 42 is electrically isolated and thus employsoptocouplers, miniature transformers, or other similar devices tomonitor the outputs of the EIR 40.

The power control voltage monitor 44 is operable to monitor the outputof the power control stage 20 to ensure its proper operation. In someembodiments, the power control voltage monitor 44 may be similar inconfiguration to the EIR voltage monitor 42, discussed above.Preferably, the power control voltage monitor 44 is operable to monitorthe output of each solid-state relay channel provided by the powercontrol stage 20. Thus, the power control voltage monitor 44 ispreferably operable to detect the failure of any SCRs 24 that comprisethe power control stage 20. The power control voltage monitor 44 ispreferably isolated in a similar manner to the EIR voltage monitor 42,and thus employs optocouplers, miniature transformers, or other similardevices to monitor the power control stage 20.

The current sensing elements 46 may be integral or discrete with thepower control voltage monitor 44 and are operable to sense the currentprovided by the power control stage 20 to ensure proper output currentdemand by the distributor, and any loads coupled therewith, and todetect conditions such as overcurrent, undercurrent, and phaseimbalance. The current sensing elements 46 may be coupled with thecontroller 16 to provide status information thereto.

The current sensing elements 46 are preferably electrically isolated andemploy current transformers or Hall-effect devices for sensing. However,in some embodiments the current sensing elements 46 may utilizeconventional shunts and optocouplers.

In delta-connected embodiments, the current sensing elements 46preferably monitor current in each of the three phases in order todetect all conditions of overcurrent, undercurrent, and imbalance.However, in wye-connected embodiments it may be desirable to monitor anyone phase and neutral, thus employing only two sensing elements.

The DC power supply 48 is operable to provide DC power to variouscontrol unit 12 components. The DC power supply 48 is preferablyoperable to couple with the 28V supply provided by conventionalaircraft. In embodiments where DC power is not available from theaircraft, the DC power supply 48 is operable to derive necessary DCpower from the alternating current supply provided by the aircraft.Thus, the DC power supply 48 may include step-down transformers andrectifiers to convert AC to DC power. The DC power supply 48 may alsoinclude filter and regulation circuitry to ensure that proper power isprovided to the control unit 12 components such as the controller 16.

The DC power supply 48 also preferably includes power-retentionelements, such as batteries, capacitors, or the like, to allow operationof the controller 16 without interrupt in the event of an AC or DCsupply power interruption from the aircraft. In some embodiments, the DCpower supply 48 is operable to power various control unit 12 componentsfor at least 200 ms when the AC or DC supply is interrupted.

The control unit 12 preferably includes a housing 50 for housing variousportions of the controller 16 and power conditioning elements 18. Thehousing 50 may be formed from various materials, including metals andplastics, to house portions of the control unit 12, such as thecontroller 16 and power conditioning elements 18. As the control unit 12is mounted on aircraft in various embodiments, and may control up toseveral kilowatts of power using solid-state techniques, the housing 50is preferably ruggedly configured for efficient thermal regulation. Asforced cooling may be difficult to provide in aircraft environments, itis preferable that the housing 50 is operable to provide appropriatethermal management using convection and radiation. Thus, the housing 50preferably includes a heatsink and/or plurality of fins 52 operable todissipate heat generated by the control unit 12.

The distributor unit 14 is rotatably coupled with the control unit 12through a rotating interface, such as one or more slip rings 54. Invarious embodiments, the distributor unit 14 is coupled to an aircraftpropeller, or other rotating component, to receive power and controlfrom the control unit 12. The distributor unit 14 is generally operableto receive the power signal from the control unit 12, utilize the powertransitions within the power signal to identify a control structure,generate a plurality of output signals corresponding to the controlstructure, and be substantially powered by the power signal. Thus, thepower signal provided by the control unit 12 provides both control andpower to the distributor unit 14.

The distributor unit 14 preferably includes a distribution controller 56and a plurality of power control elements 58 coupled with thedistribution controller 56. The distribution controller 56 is generallyoperable to identify power transitions within the power signal andinitiate proper switching of the power control elements 58 based on theidentified power transitions.

The distribution controller 56 may comprise various computing devices,microprocessors, microcontrollers, digital signal processors,programmable logic devices, integrated circuits, discrete digital andanalog logic elements, combinations thereof, and the like. Further, thedistribution controller 56 may be operable to control the variousfunctions of the system 10 and/or distributor unit 14 according to acomputer program, including one or more code segments or otherinstructions, or with various controller logic and structure.

In various embodiments and as shown in FIG. 6, the distributioncontroller 56 includes power-on-reset circuitry 60, sequence detectcircuitry 62, a counter 64, clarification delay circuitry 66, and apower supply 68. However, the distribution controller 56 may include anyelement or combination of elements operable to be powered by the powersignal and control the power control elements 58 to provide a pluralityof output signals corresponding to the power transitions within thepower signal.

The power supply 68 is operable to receive the power signal from thecontrol unit 12 to condition the power signal for use by otherdistribution controller 56 elements. For instance, in embodiments wherethe power signal is a three-phase AC signal, the power supply 68 isoperable to transform the three-phase AC signal into a DC signal for useby the other distribution controller 56 elements. Thus, in someembodiments the power supply 68 may be similar to the DC power supply 48utilized by the control unit 12. The power supply 68 may also includefiltering and regulation elements to filter and regulate the provided DCsignal. Preferably, the power supply 68 also includes power-retentionelements, such as batteries or capacitors, to enable temporary operationof the distribution controller 56 should the power signal beinterrupted.

The sequence detect circuitry 62 is operable to identify the powertransitions within the power signal and provide debouncing and filteringto enable distinction between normal power interruptions and the powertransitions. The sequence detect circuitry 62 is preferably coupled withthe power supply 68 and operable to generate a clock signal for cyclingthe counter 64. For instance, for each on-off, off-on, on-off-on,off-on-off, etc., power transition within the power signal, the sequencedetect circuitry 62 may be operable to generate a clock signal to cyclethe counter 64 to the next state. The sequence detect circuitry 62 mayinclude any circuitry operable to identify the power transitions withinthe power signal and provide a corresponding output for use by thecounter 64 or other system 10 elements. Thus, the sequence detectcircuitry 62 is not limited to the configuration illustrated in FIG. 6.

For example, in some embodiments where the power signal is an AC signal,the sequence detect circuitry 62 may be operable to detect on and offcycles and periods within the AC signal. Specifically, the sequencedetect circuitry 62 may be configured to identify the number of ACcycles the power signal is off and instruct the counter 64 to cycleappropriately. For instance, the sequence detect circuitry 62 mayidentify an off period corresponding to one AC cycle and generate asignal to cause the counter 64 to cycle one state, identify an offperiod corresponding to two AC cycles and generate a signal to cause thecounter 64 to cycle two states, etc.

In various embodiments, the sequence detect circuitry 62 is operable toutilize a time constant, where power transitions within the power signalhaving durations less than the time constant are ignored by the sequencedetect circuitry 62 and do not result in a clock signal transition. Forinstance, in embodiments where the time constant is 200 ms, the sequencedetect circuitry 62 is operable to ignore on-off-on power signaltransitions lasting less than 200 ms while on-off-on transitions lastingbetween 200 ms and 250 ms may cause a transition in the clock signal tocycle the counter 64. As should be appreciated, any time constant may beemployed by the sequence detect circuitry 62 to enable properidentification of power transitions.

The sequence detect circuitry 62 may be integral with the counter 64 insome embodiments and/or comprise any circuit element or combination ofcircuit elements, including the various components illustrated in FIG.6. In the embodiment shown in FIG. 6, the D2/R1 path is operable torapidly charge capacitor C4, while the R1/C4 combination providesfiltering against rapid spikes and transients. The output of the D2/R1and R2 paths is buffered to feed the clock input of the counter 64. Whenthe power signal ceases, capacitor C4 is discharged through R2 and R8.

The counter 64 is preferably a divide-by-n counter operable to provide aplurality of control output signals corresponding to the clock signalprovided by the sequence detect circuitry 62. In some embodiments, thecounter 64 may provide the plurality of control output signals bydirectly identifying the power transitions within the power signal. Eachcontrol output signal may correspond to the output signals provided bythe distributor unit 14, such that for each output signal the counter 64provides a control output signal. However, as shown in FIG. 6, thecontrol output signals do not necessarily correspond to each outputsignal as the counter 64 may provide a plurality of dwell states that donot correspond to the generation of output signals.

While the counter 64 is one element operable to facilitate generation ofthe desired output signals based on the power transitions within thepower signal, it should be appreciated that other logic and elements maybe utilized to effect a change in the output signals. For example, insome embodiments a state machine may be employed to jump to any statebased on the identified power transitions. Similarly, the counter 64 maybe configured to non-sequentially cycle through the states based on theidentified power transitions.

In embodiments where the distributor unit 14 provides four outputsignals, the counter 64 may provide eight states operable to cycledthrough according to the power transitions within the power signal, asidentified by the sequence detect circuitry 62. In such embodimentswhere the number of counter 64 outputs is twice the number ofdistributor unit 14 output signals, every other counter 64 state ispreferably a dwell state that is not utilized by other system 10components.

The power-on-reset circuitry 60 generally ensures that the sequencingprovided by the counter 64 conforms to a predetermined pattern alwaysstarting with the same initial output. Specifically, the power-on-resetcircuitry 60 is operable to identify power transitions, such ason-off-on transitions, within the power signal exceeding a predeterminedthreshold and reset the counter 64 accordingly. For example, in someembodiments the power-on-reset circuitry 60 is operable to identifyon-off-on transitions within the power signal that exceed 250 ms andprovide a reset signal to the counter 64, as shown in FIG. 6, such thatthe counter 64 will revert to its lowest state.

The power-on-reset circuitry 60 may include any circuit element orelements operable to provide the reset functionality discussed above. Inthe embodiment of FIG. 6, the input to U5A is held low by R5 and theinput to U5C is held low by R3 when no power is applied by the powersignal. When the power signal first applies power, the input of U5A seesa nearly instantaneous logic high as capacitor C1 is charged throughdiode D1. The nearly instantaneous logic high produces a brief pulse,determined by the C2/R3 time constant, which is buffered through thereset input of the counter 64. When the power signal ceases, the inputto U5A is held in place by C1 but is discharged through R5. The R5/C1value is preferably chosen to correspond to a desired duration of alegitimate loss of power, such as the 250 ms threshold discussed above.If the power signal resumes before C1 discharges then the counter 64 isnot reset but if the power signal resumes after C1 discharges, thecounter 64 is reset to ensure proper operation of the distributor unit14.

The clarification delay circuitry 66 is coupled with the counter 64 anddelays the control output signals to ensure that they are consistentwith the power transitions provided by the control unit 12. Inparticular, the clarification delay circuitry 66 provides aclarification delay to at least some of the control output signalsbefore they are provided to the power control elements 58, therebyensuring that the control output signals appropriately correspond to thepower transitions within the power signal provided by the control unit12.

For example, if the power signal includes a fault or a power transitionindicating that a particular control output signal should be skipped,the clarification delay circuitry 66 is operable to delay propagation ofthe control output signals until the sequence detect circuitry 62 andcontroller 64 provide appropriate outputs. Thus, the clarification delaycircuitry 66 enables the distributor unit 14 to provide the outputsignals in any order even when a sequential counter is employed.

The clarification delay circuitry 66 may include any circuit element orcombination of circuit elements operable to delay the control outputsignals provided by the counter 64. For example, in the embodiment ofFIG. 6, the OR gates detect when a control output signal has beenprovided and the C4/C3 combination provides the clarification delay timeto inhibit the application of power by providing an enable signal to thepower control elements 58.

The power control elements 58 are coupled with the distributioncontroller 56 to receive the control output signals therefrom and withthe slip rings 54 to receive the power signal therefrom. Utilizing thecontrol output signals, the power control elements 58 provide thedesired output signals by switching according to the power transitionswithin the power signal provided by the control unit 12.

The power control elements 58 are preferably coupled with theclarification delay circuitry 66 to receive the enable signal therefromand provide the output signals only when the enable signal is enabled,e.g. when the enable signal corresponds to a logic high. For instance,as shown in FIG. 6, the power control elements 58 may include aplurality of AND gates, coupled with at least some of the control outputsignals and the enable signal, such that the power control elements 58provide the desired output signals only when the enable input is high.However, as should be appreciated, any electrical elements may be usedto disable and enable the power control elements 58 and the powercontrol elements 58 do not necessarily utilize the enable signal in allembodiments.

Various embodiments of the power control elements 58 are shown in detailin FIGS. 7 and 8. Some of the power control elements 58 may be similaror identical to the power control stage 20 provided by the control unit12. Specifically, the power control elements 58 may include aback-to-back SCR configuration for each phase of the power signal, asshown in FIG. 8, to appropriately switch the power signal to provide thedesired output signals according to the control output signals providedby the counter 64. However, the power control elements 58 may includeany switching elements, such as relays or the like, operable to switchor control the power signal according to the control output signalsprovided by counter 64, and are not limited to the SCR configurationdiscussed above.

The distributor unit 14 preferably includes a housing 70 for housingvarious portions of the distribution controller 56 and power controlelements 58. The housing 70 may be formed from various materials,including metals and plastics. As the distributor unit 14 is mounted onaircraft in various embodiments, and may control up to several kilowattsof power using solid-state techniques, the housing 70 is preferablyruggedly configured for efficient thermal regulation. As forced coolingmay be difficult to provide in aircraft environments, it is preferablethat the housing 70 is operable to provide appropriate thermalmanagement using convection and radiation. Thus, the housing 70preferably includes a heatsink and/or plurality of fins 72 operable todissipate heat generated by the distributor unit 14.

Further, as the distributor unit 14 is preferably configured formounting to a rotating element, such as an aircraft propeller, thevarious distributor unit 14 components are preferably potted within thehousing 70 to provide protection from high G forces. Further, thevarious distributor unit 14 components are preferably balanced withinthe housing 70 so as to not interfere with rotation of the rotatingelement.

The distributor unit 14 may be coupled with a plurality of load devicesto provide electrical power thereto according to the power transitionsprovided by the power signal. In some embodiments the distributor unit14 may be coupled with a plurality of deicing zones 74 eachcorresponding to one or more deicing elements. For example, as shown inFIG. 12, each blade on an aircraft propeller may correspond to a heatingzone or a portion of a heating zone, to enable the blades to bedesirably deiced or heated separately. Thus, the output signals providedby the distributor unit 14 may be provided to the zones 74 to power oneor more corresponding deicing elements.

In operation, the control unit 12 is coupled with one end of a rotatinginterface and the distributor unit 14 is coupled with the other end ofthe rotating interface and configured to receive the power signal fromthe control unit 12. The control unit 12 provides the power signal, withthe plurality of power transitions therein, to both power thedistributor unit 14 and cause the distributor unit 14 to generate theoutput signals in a desired manner.

In various embodiments, the power transitions within the power signaldefine a control structure for the output signals generated by thedistributor unit 14. The distributor unit 14 is operable to identify thetransitions within the power signal, form the control structure based onthe identified power transitions, and generate the output signalsaccordingly. For example, if the distributor unit 14 is operable toprovide four outputs, the control unit 12 may form the power signal andpower transitions to represent a particular control structure, such asan output sequence or output combination, and the distributor unit 14may identify the power transitions to form the control structure andgenerate the appropriate output sequence or combination.

Thus, by including on-off transitions, off-on transitions, on-off-ontransitions, off-on-off transitions, combinations thereof, and the like,within the power signal, the control unit 12 is operable to dictate thecontrol structure for the output signals generated by the distributorunit 14. The control unit 12 and distributor unit 14 may employ anysignaling method using power transitions to identify and form thecontrol structure.

The control structure may correspond to a load sequence for a pluralityof load devices, such as deicing zones 74 or deicing elements, coupledwith the distributor unit 14. For example, the control structure maydictate the sequence in which the load devices are powered, thecombination of load devices which are utilized, the duration each loaddevice is powered, combinations thereof, and the like.

Preferably, the control structure formed by the distributor unit 14utilizing the power transitions corresponds to the various statesprovided by the counter 64. Thus, for example, the sequence detectcircuitry 62 may identify a power transition within the power signal andinstruct the counter 64 to cycle to the next state. In embodiments wherethe counter 64 is operable to cycle through eight states, the sequencedetect circuitry 62 may identify a power transition, or a combination ofpower transitions, to cycle through each of the eight states.

In such embodiments, the counter 64 is operable to provide eight controloutput signals corresponding to eight states, and the power controlelements 58 are operable to provide four output signals using the eightcontrol output signals. For example, the eight states provided by thecounter 64 may correspond (in order) to: dwell, a first output signal,dwell, a second output signal, dwell, a third output signal, dwell, anda fourth output signal. Utilizing the power transitions, the distributorunit 14 is operable to cycle through each of these states to provide thedesired output signals. As discussed above, the power-on-reset circuitry60 is operable to reset the counter 64 to the first state should certainconditions be satisfied.

In various embodiments, the system 10 utilizes on-off-on powertransitions to cycle through the various states provided by the counter64. For instance, for each on-off-on power transition within the powersignal, the counter 64 may cycle to the next state thereby causing thedistributor unit 14 to output a different output signal, a differentcombination of output signals, or no output at all.

Preferably, the counter 64 cycles to the next state only if theidentified on-off-on transition has a duration within a predeterminedrange. For instance, as discussed above, the sequence detect circuitry62 may employ a time constant, such as 200 ms, such that on-off-ontransitions lasting between 200 ms and 250 ms cause the counter 64 tocycle to the next state while on-off-on transitions having otherdurations do not cause the counter 64 to cycle to the next state. Oncethe counter 64 cycles to a new state in response to a power transition,the counter 64 may stay in the new state, such that the distributor unit14 outputs the same output signal for any period of time. As should beappreciated, in embodiments where the distributor unit 14 is coupledwith the deicing zones 74, it may be desirable to limit state durationfor temperature control scheduling purposes. Upon detection of the nexton-off-on transition having a duration within the predetermined range,the counter 64 may cycle to the next state.

As discussed above, on-off-on transitions having durations less than thetime constant, such as less than 200 ms, are preferably ignored by thedistributor unit 14 to prevent temporary interruptions in the powersignal from interfering with the generation of output signals. As isalso discussed above, on-off-on transitions having durations greaterthan the predetermined range, such as 250 ms, are preferably identifiedby the power-on-reset circuitry 60 to reset the counter 64.

In some situations, such as where a particular deicing zone fails, itmay be desirable to skip over a faulty zone by not providing an outputsignal corresponding to the zone, while still maintaining the controlstructure associated with the overall sequence provided by the powersignal. To provide such functionality, the system preferably utilizesthe clarification delay discussed above regarding the clarificationdelay circuitry 66. In particular, the distributor unit 14 provides theclarification delay, where the output signal is inhibited for durationof the clarification delay after the counter 64 has cycled to the nextstate. Thus, at any time during the clarification delay, an on-off-onsequence may be initiated to cycle the counter 64 to avoid generation ofa particular output signal. Further, should fault detection devices andmonitors included within the control unit 12 activate, the control unit12 can generate another on-off-on transition within the clarificationdelay period to prevent the generation of a particular output signal.

As shown in FIG. 2, the duration of the last dwell in the cycle ofstates provided by the counter 64 is preferably equal to the remainderof time in the cycle period. Varying the duration of the last dwell in acycle allows the distributor unit 14 to provide consistent cycle timingeven if one or more states are skipped due to faults or otherconditions.

As should be appreciated, the system 10 may employ any control methodutilizing power transitions within the power signal and is not limitedto the on-off-on transition methods discussed above. Further, the powertransition methods employed by the system 10 may be modified withoutaltering the physical components of the system 10, such that differentcontrol structures and output signals may be provided without requiringreplacement of the system 10.

Although the invention has been described with reference to thepreferred embodiment illustrated in the attached drawing figures, it isnoted that equivalents may be employed and substitutions made hereinwithout departing from the scope of the invention as recited in theclaims.

For example, as shown in FIG. 9, in various embodiments the control unit12 may provide DC power to the distributor unit 14 through the rotatinginterface instead of three-phase or one-phase AC power. In suchembodiments, two slip-rings may be employed as the rotating interfaceinstead of the three-slip rings required for three-phase AC power. Toprovide DC power to the distributor unit 14, the control unit 12preferably includes an AC/DC converter to convert AC power provided byexternal sources, such as the aircraft, to DC power for use by thedistributor unit 14.

For example, the control unit 12 may include a six-pulse rectifier toconvert AC to DC power. However, such a configuration may be undesirabledue to the harmonics produced from the configuration, which may exceedindustry standards and manufacturing requirements. Thus, as shown inFIGS. 9 and 10, a multiphase transformer rectifier 76 is preferablyutilized to convert three-phase AC power, provided by the aircraft, intoDC power for use by the distributor unit 14. The multiphase transformerrectifier 76 complies with required harmonic, power factor, and emissionrequirements and is preferably capable of operating from a variablefrequency supply. In situations where isolation is not required, anautotransformer 78 may be employed as it provides the lowest weight ofAC/DC converter implementations. Alternatively, active power factorcorrection (PFC) circuitry may be utilized in connection with arectifier to convert three-phase AC power to DC in a manner thatcomplies with harmonic and power factor requirements.

Having thus described the preferred embodiment of the invention, what isclaimed as new and desired to be protected by Letters Patent includesthe following:

1. A system for powering and controlling de-icing elements on aircraftpropellers, the system comprising: a control unit operable to receivepower from a three-phase power source and to switch the power on andcompletely off with a series coupled switching element to generate apower signal having a plurality of power transitions, wherein at leastone of the power transitions has a time duration different than otherpower transitions; and a distributor unit operable to- rotatably couplewith the control unit, receive the power signal from the control unit,power at least a first de-icing element with the power signal, identifya power transition of a first time duration, during the first powertransition, apply no power to the de-icing elements, identify subsequentpower transitions of a second time duration equal to or shorter than thefirst time duration, and, in response to the subsequent powertransitions, switch the power signal to at least a second de-icingelement.
 2. A system for powering and controlling de-icing elements onaircraft propellers, the system comprising: a control unit operable togenerate a power signal having a plurality of power transitions; and adistributor unit operable to- rotatably couple with the control unit,receive the power signal from the control unit, power at least one ofthe de-icing elements with the power signal, identify power transitionswithin the power signal, and generate a plurality of output signalscorresponding to the identified power transitions to select which of thede-icing elements to power with the power signal and to switch the powersignal to different de-icing elements when the output signals change dueto the identified power transitions in the power signal.
 3. An aircraftpropeller de-icing system comprising: a control unit including- an inputfor receiving a power signal from an aircraft power supply, a controldevice and power conditioning elements coupled with the input forreceiving the power signal and for converting it to a power signalhaving a plurality of power transitions corresponding to a controlscheme; and a distributor element coupled with the control unit with atleast one slip ring and including- an input for receiving the powersignal from the control unit, a control device operable to identify thepower transitions within the power signal and to generate a plurality ofoutput signals corresponding to the identified power transitions, and aplurality of power control elements operable to apply the power signalto at least one of the de-icing elements and to switch the power signalto a different de-icing element when the output signals change due tothe identified power transitions in the power signal.
 4. An aircraftpropeller de-icing system comprising: a control unit including- an inputfor receiving a power signal from an aircraft power supply, a controldevice and power conditioning elements coupled with the input forreceiving the power signal and for interrupting it when current suppliedby the power signal is near zero to create a power signal having aplurality of power transitions; and a distributor element coupled withthe control unit with at least one slip ring and including- an input forreceiving the power signal from the control unit, a control deviceoperable to identify the power transitions within the power signal andto generate a plurality of output signals corresponding to theidentified power transitions, and a plurality of power control elementsoperable to apply the power signal to at least one of the de-icingelements and to switch the power signal to a different de-icing elementwhen the output signals change due to the identified power transitionsin the power signal.
 5. A system for powering and controlling de-icingelements on aircraft propellers, the system comprising: a control unitincluding a switching element interposed in series between an aircraftpower source and a load to generate a power signal having a plurality ofpower transitions; and a distributor unit operable to- rotatably couplewith the control unit, receive the power signal from the control unit,power at least one of the de-icing elements with the power signal,identify power transitions within the power signal, and generate aplurality of output signals corresponding to the identified powertransitions to select which of the de-icing elements to activate and toactivate a different de-icing element when the output signals change dueto the identified power transitions.